Characteristics of anaerobic-digested manureAnaerobic digestion: A way to enhance
nutritional performance of animal manure
Torben Ravn PedersenNational SpecialistBiogas and Slurry Separation
Subejcts
• Danish Agricultural Advisory Service
• Manure handling in Denmark
• Biogas in Denmark
• Nutritient value in treated manure
Danish Agricultural Advisory Service
Manure types in Denmark
79%
5%
5%
11%
Slurry
Urine
Farm yard manure
Deep litter
How is slurry spread in Denmark?
0%
68%
32%
Broadspreading
Trailing hoses
Direct injection
About 60 farmscale biogas plants in Denmark
20 centralized biogas plants
Biogas rests on tree legs
Biogas
Energy EnvironmentAgriculture
Agricultural advantages
• Improved fertilizer value of nitrogen
• Balanced P and K-balance in slurry
• Homogeneous and light fluid
• Full declaration of nutrients
• Bacteria-free and seedless
• Reduced costs for transportation of slurry
Environmental advantages
• Reduced nitrate leaching
• Reduced odour problems
• Reduced green house gas emission
• Controlled recycling of organic waste (turns waste into valuable fertilizer)
Mixing and digesting slurry change the characteristic of
the slurryDM,
%
N-tot,
kg/t
NH4-N,
kg/t
P,
kg/t
K,
kg/t
pH NH4-N, %
Digested slurry
Pig slurry
Cattle slurry
4,8
5,0
7,5
4,4
4,8
3,9
3,5
2,9
2,4
1,0
1,1
0,9
2,3
2,3
3,5
7,6
7,1
6,9
81
74
61
Ammonia evaporation in spring barley
0
10
20
30
40
50
2002 2003
NH
3-lo
ss, %
of s
prea
d N
H4-N
Untreated pig slurry Digested pig slurry
Improved fertilizer effect of nitrogen- trials in winter wheat
0 20 40 60 80 100
Cattle slurry, injected
Pig slurry, injected
Digested slurry, injected
Cattle slurry, trailing hoses
Pig slurry, trailing hoses
Digested slurry, trailing hoses
N-utilization, % (fertilizer equivalent)
Fertilizer value
Fertilizer plan for nitrogen for 1 ha grass
250250N-requirement, kg
170170N in slurry, kg total
6040N-utilization, %
10268N- in slurry, utilized, kg
34
27
-
-
Saved, kg
Saved, Euro
148182Mineral fertilizer
Digested slurryCattle slurry
Per hectare
N, P, and K in mineral fertilizer
0
20
40
60
80
100
120
140
160
1930 1940 1950 1960 1970 1980 1990 2000 2010
Kg
per
hec
tare
NPK
Pro
gno
sis
N-application in Denmark
0
50
100
150
200
250
300
350
400
450
1940 1950 1960 1970 1980 1990 2000 2010
1,00
0 to
nne
of N
per
yea
r
FertilizerManure
Injection in bare soil
Injection of slurry in grass
Digested slurry is low on bacteria
<5<5<5<5<5
1,300,000140,000690,000
9,000,00062,000
Mar. 18May 13July 15Sept. 9Nov. 11
AfterBeforeDate
Test results from Ribe Biogas,bacteria per ml. slurry (1998)
Log 1
0 ge
rms
per
ml.
slur
ry
Time, weeks
Slurry tank, 6-8°C Mesofile biogas, 35°CThermofile biogas, 53°C
10
6
5
3
Digestion reduces odour
Slurry separation –on treated manure
Fot
o:
Wes
tfal
ia
Fot
o:
Big
ada
n A
/S.
Thank you for your attention!
